Passive high pass filter - Marchand XM446XLR-A

Thanks guys for the responses so far.  bdp24, I believe you are talking about Marchand's active crossovers but I am not interested in putting another active component in the signal chain.  Thank you for referencing the First Watt B4.  Even though it is an active device, it was still interesting to read the manuals by Pass.  It would be interesting ot me if he would offer a passive kit that the user could stuff with their favorite caps and resistors, and to provide some technical information on component compatibility and matching subs to the main speakers.

I have not yet read anything saying the Marchand passive high pass filter is exceptional, or does nothing unwanted to the signal.  Instead, what I have mostly read is that some prefer the Marchand high pass to doing nothing because they believe reducing the demand for the main amplifier to drive low frequencies improves clarity in the upper frequency ranges.  The flavor of most of the posts seems to be that one way or the other is a lesser of two evils.

I am really interested in hearing from folks with a high end and resolving system who are using monitor type main speakers mated with subs, and the method they have found to best cross over the subs to the mains.

One advantage I have is that my subs and main speakers come from the same manufacturer and are made to work together.  There is an option to use a crossover within the subs to high pass the main signal so that is something else I can at least try, particularly if I position the subs near the main speakers so the second IC from the subs to the mains would be short.

Now that I have finally received the main speakers, second sub and stands for everything, I will contact the manufacturer to verify their recommendation for the best way to integrate the high and low frequencies.  Would still appreciate hearing about success stories.

Thanks bdp24, I have calculated the capacitor size needed but everything I have read seems to be for single-ended signals.  If I want to go the single capacitor route with my balanced amp, do you know what I would do differently...i.e., do I put a series cap on both of the differential signal legs?  Is the calculation different for a balanced signal?

Thanks much Al!
The Claytons only have balanced inputs so I am confident the 100K input impedance is for the balanced condition.
Good point on matching the caps.  I plan to try something relatively high quality like Jupiter copper film caps.
Partsconnexion will match them for $1 per pair.
I plan to try 0.022uf caps for a cut-off frequency of about 72 Hz and then start by low-passing the subs at 80 Hz.
The next cap size up (0.047uf) gives a cut-off frequency that is a little low at 34Hz but may still be an option.
If I wanted something in-between, could I series the 0.022 with a 0.01 cap?
Caps are thankfully 25% off this month, which is good since I need four of them.

Thanks again Al.  It seems the 0.047uf caps will be a good start.  If the cut-off is at 68Hz then that will actually be perfect and if it is at 34Hz then it still relieves the amplifier from trying to drive the lowest frequencies.  Another thing I could do is to try some less expensive caps first to determine the correct value, and then later move up to the caps I want to use.

I also appreciate the analysis and technical information because one of my favorite things about this site is learning about stuff I don't fully understand.

In summary, there doesn't seem to be anything close to a universal answer to this situation.  I have decided not to pursue a Marchand filter at this time because I don't want something in the path that may negatively affect the signal going to my main speakers.  The subs do have a (reportedly) high quality on-board high pass filter so I can give that a try.  The single cap in-line interests me and I may give that a try.  If it works well, I could actually wire them inside of my preamp, or make a pair of balanced cables with the capacitors in-line.  From what I have read, it doesn't seem to matter where the caps are placed as long as they are between the preamp output and the amplifier input.  Some put them inside the input of the amplifiers.

Thanks for everyone for the comments and help.